Annotate static variables cpuidle_state_table and mwait_substates
with __initdata, because they are only used during the initialization
of the driver.

Also notice that static variable icpu could be annotated analogously
and the structure pointed to by it could be __initconst, but two of
its fields are accessed via icpu in intel_idle_cpu_init() and
auto_demotion_disable(), so introduce two new static variables,
auto_demotion_disable_flags and disable_promotion_to_c1e, to hold
the values of these fields, set them during the initialization and
use them in those functions instead of accessing the source data
structure via icpu.

That allows icpu to be annotated with __initdata, so do that,
and it will also allow some __initconst annotations to be added
subsequently.

No intentional functional impact.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>